The NIH is one of eight centers in this prospective, multi-center, double-blind, randomized, placebo-controlled study. The objective is to determine the safety and efficacy of nitric oxide for inhalation in the treatment of vaso-occlusive pain crisis in patients with sickle cell disease. The study population will include patients with sickle cell disease (SS, S-beta-Thalassemia) presenting with vaso-occlusive pain crisis. Patients will be 10 years of age or above and will be administred either placebo or inhaled nitric oxide to see if the experimental agent, inhaled nitric oxide, can reduce the time it takes for resolution of the vaso-occlusive crisis. We began pre-enrolling in January 2005 and to date have pre-enrolled 54 patients. Of these 54 patients, 16 have actually enrolled and been treated in the study and an additional 5 more who were not pre-enrolled have been treated in the study. We anticipate pre-enrolling approximately 200 patients and enrolling and treating 50 of the pre-enrolled patients. Due to the double-blind nature and the design of this trial, no preliminary data analysis will be available until completion of the entire study.[unreadable] The other participating sites have also began enrollment. This brings the number of subjects pre-enrolled to 92 and the number of subjects enrolled in the treatment study to 42.